Photoreceptor changing apparatus for electrophotographic copying machines

ABSTRACT

A photoconductive strip wound on a supply reel and a take-up reel is contained in a cylindrical supporter and paid out of the supply reel and applied to the outer periphery of the supporter so that a portion of the photoconductive strip disposed on the outer periphery serves as a photoreceptor of the photosensitive drum. When the portion of the photoconductive strip serving as a photoreceptor is fatigued after being used in several copying operations, the photoconductive strip is advanced in a predetermined length so that the portion of the photoconductive strip on the outer periphery is wound on the take-up reel and a fresh portion of the strip can be applied to the outer periphery of the cylindrical supporter to change the photoreceptor on the photosensitive drum. Counter means is provided and operates in association with the take-up roller to indicate the length of the residual photoconductive strip on the supply reel or produces a strip exhaustion signal when no strip is wound on the supply reel.

United States Patent Nagahara PHOTORECEPTOR CHANGING APPARATUS FOR ELECTROPHOTOGRAPHIC COPYING MACHINES [75] Inventor: Yasumori Nagahara, Yokosuka,

Japan [73] Assignee: Ricoh Co., Ltd., Tokyo, Japan [22] Filed: July 19, 1973 [21] Appl. No.: 380,550

[30] Foreign Application Priority Data July 31, 1972 Japan 47-76718 July 31, 1972 Japan 47-76719 Aug. 3, 1972 Japan 47-78131 Aug. 3, 1972 Japan 47-78132 [52] U.S. Cl 355/3 R [51] Int. Cl. G03G 5/10 [58] Field of Search 355/3, 16, 64

[56] References Cited UNITED STATES PATENTS 2,496,329 2/1950 Briechle 355/64 3,480,361 11/1969 Doi 3,706,489 12/1972 Moxness 355/3 Primary ExaminerJohn M. Horan Attorney, Agent, or Firm-Cooper, Dunham, Clark, Griffin & Moran [5 7] ABSTRACT A photoconductive strip wound on a supply reel and a take-up reel is contained in a cylindrical supporter and paid out of the supply reel and applied to the outer periphery of the supporter so that a portion of the photoconductive strip disposed on the outer periphery serves as a photoreceptor of the photosensitive drum. When the portion of the photoconductive strip serving as a photoreceptor is fatigued after being used in several copying operations, the photoconductive strip is advanced in a predetermined length so that the portion of the photoconductive strip on the outer periphery is wound on the take-up reel and a fresh portion of the strip can be applied to the outer periphery of the cylindrical supporter to change the photoreceptor on the photosensitive drum. Counter means is provided and operates in association with the take-up roller to indicate the length of the residual photoconductive strip on the supply reel or produces a strip exhaustion signal when no strip is wound on the supply reel.

US. Patent Dec. 16,1975 Sheet10f6 3,926,515

US. Patent Dec. 16, 1975 Sheet 2 of6 3,926,515

US. Patent Dec. 16,1975 Sheet30f6 3,926,515

U.S. Patent Dec. 16, 1975 Sheet40f6 3,926,515

US. Patent Dec.16,1975 Sheet5of6 3,926,515

U.S. Patent Dec. 16, 1975 Sheet6of6 3,926,515

PHUTORECEPTOR CHANGING APPARATUS FOR ELECTROPHOTOGRAPHIC COPYING MACHINES BACKGROUND OF THE INVENTION This invention relates to photoreceptor changing apparatus for electrophotographic copying machines, and more particularly it is concerned with a photoreceptor changing apparatus for an electrophotographic copying machine of the type using a photosensitive drum having an organic semiconductor strip. A strip coated with zinc oxide or other flexible photoconductive material is stored in the photosensitive drum and a portion of the strip is wound on the periphery to serve as a photoreceptor, the apparauts being effective to automatically replace the old photoreceptor with a new photoreceptor from time to time.

In an electrophotographic copying machine using a photosensitive durm having an organic semiconductor or other photoconductive material layer formed on the surface of a cylindrical supporter, the photoconductive material layer of the photosensitive drum is exposed to a current of about 700 volts when it is charged. Charging is effected each time copying is carried out, so that the photoconductive material layer suffers fatigue from discharge breakdown after about 5,000 copying operations are performed. When the photoconductive material layer is in this condition, it shows a markedly lowered efficiency in forming electrostatic latent images and transferring the formed images to copy sheets, and it becomes impossible to produce duplicates of high quality. This means that the photosensitive drum must be replaced by a new one.

It is troublesome to perform the operation of replacing the old photosensitive drum with a new one. Thus, proposals have been made to form the photoconductive material layer in the form of a flexible sheet or strip and apply this sheet or strip of photoconductive material to the outer periphery of a cylindrical supporter to provide a photosensitive drum, so as to facilitate changing of the photoconductive material layer alone without needing to change the photosensitive drum as a whole.

When the photoconductive material layer is in strip form, the strip of photoconductive material is wound at one end on a supply reel in the cylindrical supporter and at the other end on a take-up reel therein. A portion of the strip paid out of the supple reel is applied to the outer periphery of the cylindrical supported, so that it serves as a photoreceptor on the photosensitive drum. When the photoreceptor gets fatigued, this arrangement permits the photoreceptor to be readily changed by actuating the take-up reel to advance the strip and wind on the take-up reel the used portion of the strip or the used photoreceptor on the outer'periphery of the cylindrical supporter and permitting the supply reel to rotate in slaved relation to feed another portion of the strip to the outer periphery so that it may serve as a new photoreceptor.

Generally, when the photoreceptor on the outer periphery of the cylindrical supporter is changed, a torque of a'high value is required to advance the photoconductive strip because the portion of the strip disposed on the outer periphery of the cylindrical supporter is maintained in intimate contact therewith and a resistance of a high value is offered to the movement of the strip. Generally, a photoconductive strip comprises an aluminum or other conductive material layer formed on a base made as of polyester film, and a layer of a mixture of polyvinyl carbazole or other organic semiconductor with a binding agent and a sensitizer, and its thickness is about 0.1 millimeter. Thus, when the photoconductive strip of a very small thickness is applied to the outer periphery of the cylindrical supporter, difficulty is experienced in moving photoconductive strip along the outer periphery because the former is stuck fast on the latter.

It has hitherto been customary to rotate the take-up reel from the drive for the photosensitive drum in order to advance the photoconductive strip on the outer periphery of the photosensitive drum. In conventional copying machines, a torque of a high value is obtained by driving the take-up reel from the drive through a speed reduction gearing. The use of the speed reduction gearing which is complex in construction poses a problem. Since it is provided in the cylindrical supporter, the photosensitive drum has a greater length than is necessary because the space required for installing the gearing should be taken into consideration in addition to the width of the photoconductive strip when the drum is designed. As a result, the drum has the disadvantages of being large in size and heavy in weight.

As aforementioned, the photoconductive strip is advanced by rotating the take-up reel when the photoreceptor is changed in the photosensitive drum constructed as described above. Thus, the diameter of the strip wound take-up reel gradually increases as the photoconductive strip on the outer periphery of the drum is advanced. This has the disadvantage of the length of the strip Wound on the take-up reel increasing each time the strip is advanced if the take-up reel is designed to make a predetermined number of revolutions for advancing the strip. Since the photoconductive strip is very expensive, it is necessary to provide means to avoid the waste of the strip. Proposals have been made to use detection means relying on a pinch roller which is brought into frictional engagement with the used portion of the photoconductive strip or the used photoreceptor returned to the interior of the cylindrical supporter, so that the take-up reel will stop rotating when the pinch roller has made a predetermined number of revolutions. The use of the pinch roller has a disadvantage in that it involves a considerably complex mechanism because the pinch roller should be mounted in the interior of the drum and the number of its revolutions should be taken out of the drum. The weight of the drum itself is increased thereby interfering with the operation of mounting or removing the strip of photoconductive material.

when the photosensitive drum is constructed as aforementioned, it would be very convenient if the length of the photoconductive strip wound on the supply reel in the interior of the cylindrical supporter is indicated by some means at the outside of the drum. Also, it would greatly facilitate handling of an electrophotographic copying machine if some means is provided for producing a signal informing that the photoconductive strip wound on the supply reel has been exhausted.

SUMMARY OF THE INVENTION An object of this invention is to provide a photoreceptor changing apparatus for electrophotographic copying machines comprising a photoconductive strip advance device comprising speed reduction means disposed outside the drum and comprising a planetary gearing, the sun gear of the planetary gearing being rotated at a rate differeing from the rate of rotation of the drum when the photoconductive strip is advanced to change photoreceptors so as to thereby produce a torque of a high value for driving the take-up reel.

The invention offers the advantage of making it possible to obtain a compact size and a light weight in a photosensitive drum because the speed reduction gearing is not disposed in the interior of the drum.

Another object of the invention is to provide a photoreceptor changing apparatus of the type described which further comprises a device for feeding a photoconductive strip in a predetermined length disposed outside the photosensitive drum, such device comprising controller, counter means actuated in association with the operation of the drive for the photosensitive drum each time the used portion of the strip on the outer periphery of photosensitive drum or the used photoreceptor is wound on the take-up reel, and a cam for automatically adjusting the length of the strip paid out of the supply reel, so that the photoconductive strip can be paid out of the supply reel in a predetermined length at all times.

The controller of the device for feeding a photoconductive strip in a predetermined length is rendered operative when the photoconductive strip is advanced along the outer periphery of photosensitive drum, and the counter means is actuated at the termination of each operation of the controller so as to adjust the length of the photoconductive strip wound on the takeup reel by moving a microswitch and compensating for an increase in the diameter of the strip wound take-up reel. This permits avoiding the waste of the photoconductive strip to be avoided which would otherwise occur if the photoconductive strip were wound on the take-up reel in a length greater than is necessary because of the increase in the diameter of the strip wound take-up reel, and makes it possible to pay out of the supply reel a predetermined length of the photoconductive strip at all times. The number of photoreceptors provided by one photoconductive strip can be made greater by at least one sheet when the copying machine incorporating the invention therein is used than when conventional copying machines are used. An added advantage offered by the use of the invention is that it is possible to obtain a compact size and a light weight in a photosensitive drum because no detection means relying on friction is provided in the interior of the cylindrical supporter.

Another object of the invention is to provide a photoreceptor changing apparatus of the type described which comprises means for indicating the length of the residual photoconductive strip on the supply reel adapted to be actuated at the termination of each operation of the counter means actuated in conjunction with the winding of the used portion of the photoconductive strip or the used photoreceptor on the outer periphery of the photosensitive drum.

This arrangement permits the length of the residual photoconductive strip on the supply reel to be readily indicated by merely having either the pointer or the graduated dial operatively associated with the counter means of the device for feeding a photoconductive strip in a predetermined length. The use of the mechanical indication means constructed as aforementioned is very convenient because the residual length indicated is still indicated even if the main switch is turned off.

A still another object of the invention is to provide a photoreceptor changing apparatus of the type described comprising means for detecting the exhaustion of a photoconductive strip on the supply reel operatively associated with the device for feeding a photoconductive strip in a predetermined length and the means for indicating the length of the residual strip on the supply reel. This feature permits the provision of detection means in the interior of the drum to be eliminated and makes it possible to combine all the devices and means of the apparatus into a single unit disposed outside the drum. Thus, the photoreceptor changing apparatus according to the invention is economical in construction because it can be detachably mounted as a unit in a copying machine using a photosensitive drum. 4

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of the photosensitive drum in explanation of the process of electrographic copying carried out with the drum;

FIG. 2 is a sectional view of the photosensitive drum taken along the line II II of FIG. 3;

FIG. 3 is a fragmentary sectional view of the photosensitive drum and portions of the photoreceptor changing apparatus according to the invention taken along the line lIIIII of FIG. 5;

FIG. 4 is an exploded perspective view of the photoconductive strip advance device of the photoreceptor changing apparatus according to the invention;

FIG. 5 is a side view of the photoconductive strip advance device of the photoreceptor changing apparatus according to the invention;

FIG. 6 is a sectional view taken along the line Vl-VI of FIG. 3;

FIG. 7 is an exploed perspective view of the photoconductive strip advance device, portions of the device for feeding a photoconductive strip in a predetermined length, means for indicating the residual photoconductive strip on the supply reel and means for detecting the exhaustion of the photoconductive strip on the supply reel;

FIG. 8 is a sectional view of the spring clutch of the device for feeding a photoconductive strip in a predetermined length;

FIG. 9 is a perspective view of essential portions of the device for feeding a photoconductive strip in a predetermined length; and

FIG. W is a front view of FIG. 9.

DESCRIPTION OF A PREFERRED EMBODIMENT First, the process of performing an electrophotographic copying operation on the outer periphery of a cylindrical supporter on which a portion of a photoconductive strip is wound and functions as a photoreceptor will be described to enable the invention to be better understood.

A photosensitive drum 8 of the electrophotographic copying machine in which the invention is incorporated comprises a cylindrical supporter 1 having an outer periphery formed therein with axial slit la and 1b. A portion of a photoconductive strip 2 is wound on a major portion of the outer periphery between the slits la and 1b and functions as a photoreceptor, so that the cylindrical supporter l and the photoreceptor constitute a photosensitive drum 8.

The photoconductive strip 2 is wound at one end portion on a supply reel 6 rotatably mounted in the interior of the cylindrical supporter 1 and disposed parallel to a shaft 3 supporting the cylindrical supporter 1. The supply reel 6 is in the form of a tubular shaft which is rotatably fitted over a support shaft 7 disposed parallel to the support shaft 3 for the cylindrical support 1 and secured to left and right side walls 10, 1d (See FIG. 3) of the cylindrical supporter l. The other end portion of the photoconductive strip 2 wound at one end portion thereof in roll form on the supply reel 6 is paid out of the supply reel 6 and extends through one slit 1b to be wound on the major portion of the outer periphery clockwise in FIG. 1 and FIG. 2. The other end of the strip extends through the other slit 1a into the interior of the cylindrical supporter 1 and wound on a take-up reel 4 disposed in a position dia metrically opposite to the position in which the supply reel is disposed. Thus, a portion of the photoconductive strip 2 is wound on the major portion of the outer periphery of the cylindrical supporter 1 and maintained in intimate contact therewith to serve as a photoreceptor.

The take-up reel 4 is also in the form of a tubular shaft which is secured to a support shaft 5 disposed parallel to the support shaft 3 for the cylindrical supporter 1 and rotatably supported by the left and right side wall 1c, 1d (See FIG. 3) of the cylindrical supporter 1. When the support shaft 5 rotates, the photoconductive strip 2 is advanced and the portion of the strip on the outer periphery of the cylindrical supporter 1 serving as a photoreceptor is withdrawn into the interior of the cylindrical supporter 1 and wound on the take-up reel 4.

The photosensitive drum 8 constructed as aforementioned rotates in the direction of an arrow c in FIG. 1 and continuously perform an electrophotographic copying or duplicating operation to produce a plurality of copies from an original. The support shaft 3 for the photosensitve drum 8 is connected to a synchronous motor (not shown) and rotated thereby at a constant rate. Rotation of the photosensitive drum 8 first renders a cleaning brush 9 operative to clean the photoreceptor on the outer periphery of the photosensitive drum 8 sothat the photoreceptor may be uniformly charged. After cleaning, charging is carried out.

A charging device 12 is disposed adjacent the brush 9 and comprises an array of corona discharge electrode or electrodes 10 connected to a high voltage power source (not shown), enclosed by a shield member 11 and disposed axially of the drum 8 across its outer periphery. An electrostatic charge is applied uniformly to the photoreceptor on the outer periphery of the photosensitive drum 8.

Disposed adjacent the charging device in the path of movement of the drum 8 is an exposure device comprising an optical system 13 for exposing the photoreceptor on the outer periphery of the drum 8 to an optical image of an original to be duplicated. By this operation, an electrostatic latent image of the original is formed on the photoreceptor by removing the charge on the exposed regions of the photoreceptor.

Disposed adjacent the exposure device is a developing device 14 provided with a developing agent 15 carrying opposite charge to the electrostatic latent image on the photoreceptor. The developing device comprises a developing agent tank 16 containing the developing agent 15 therein, and a magnetic brush 17 rotatably supported in the tank 16. The developing agent 15 adhering to the surface of the magnetic brush 17 rotating in the direction of an arrow Y is supplied to the electrostatic latent image on the photoreceptor on the photosensitve drum 8 so that a toner adheres to the image to form a toner image of the original.

Disposed adjacent the developing device is an electrostatic transfer printing device 20 for printing a toner image on a copy sheet or a support surface by transfer printing from the photoreceptor on the photosensitive drum 8. More specifically, the toner image formed on the photoreceptor is transferred to a transfer printing sheet 18 made of paper or other suitable material and automatically fed by a pair of copy sheet feed rollers 19a, 19b to be brought into direct contact with the toner image on the photoreceptor, so that the toner image is transferred from the photoreceptor to the copy sheet 18 by the electrostatic transfer printing device 20. The transfer printing device 20 is of the same type as the charging device 12 and comprises an array of corona discharge electrodes 21 and shield member 22. The device 20 produces an electrostatic charge for electrostatically attracting the toner image from the photoreceptor to the surface of the transfer copying sheet 18.

Although the embodiment is shown and described as using an electrostatic transfer printing device 20 for effecting transfer printing of a toner image, it is to be understood that the device 20 may be replaced by a pressure transfer printing device which effects transfer printing of a toner image by applying pressure to the surface of a transfeer printing sheet opposite to the surface thereof which is brought into engagement with the toner image. Alternatively, the two devices may be used in combination.

Disposed adjacent the transfer printing device is a printed sheet stripping device for picking the printed sheet off the photoreceptor on the outer periphery of the drum 8. As shown, the printed sheet stripping device comprises a suction cylinder 23 for drawing a leading end portion 18a of the printed transfer printing sheet 18 by suction to pick it off the photoreceptor with which the sheet 18 is in intimate contact. The printed transfer printing sheet 18 picked off the photoreceptor by the suction cylinder is guided by a guide 24 to move to an image fixing device (not shown).

An example of the electrostatic copying machines of the transfer printing type in which the present invention can be incorporated has been outlined above. The construction of the photosensitive drum 8 will be described more in detail. The left and right side walls 1c and 1d of the photosensitive drum 8 having built in its interior the supply reel 6 and the take-up reel 4 for the photoconductive strip 2 are formed with recesses 1e and 1f respectively in the central portion as shown in FIG. 3. The support shaft 3 extends through the central portion of the recesses 1e and 1 f, and the support shaft 3 is connected to the recess he by a short cylinder 26. The short cylinder 26 is formed therein with a V- groove 26a oriented axially of the support shaft 3 and receiving therein a rivet 27 threaded into the support shaft 3, and has a flange 26b formed at one end which is secured to the bottom of the recess 12 by a screw 28. Thus, the photosensitive drum 8 rotates as a unit with the support shaft in a predetermined direction,

The photosensitive drum 8 adapted to rotate as a unit with the support shaft 3 in a predetermined direction is disposed between immovable side plates 25a and 26b of the copying machine. The support shaft 3 is journalled at one end portion by bearings 31 and 33 housed in a cylindrical bearing housing 29 secured to one side 7 plate a and at the other end portion by a bearing housed in a short cylindrical bearing housing 30 secured to the other side plate 25b, so that the photosensitive drum 8 is rotatably supported between the two side plates 25a and 25b.

More specifically, the cylindrical bearing housing 29 secured to one side plate 25a extends inwardly at its forward end portion. into the recess 16 formed in one side wall 1c of the drum 8. A left half portion 3a (in FIG. 3) of the support shaft 3 extends through the bearing housing 29 and out of the side plate 25a, and journalled by the bearings 31 and 33 housed in the bearing housing 29. A right end portion 3b (in FIG. 3) of the support shaft 3 is joumalled by the bearing 32 housed in a bearing housing 30 secured to the inner surface of the other side plate 25b. The right end portion 3b of the support shaft 3 is formed therein with an axial threaded bore 3c for threadably receiving therein a knob 34 through an opening 250 formed in the other side plate 25b. An extension coil spring 35 is mounted through a tubular member 36 on a portion of the support shaft 3 between the bearing 32 and the right side wall 1 d of the drum 8. By turning the knob 34, it is possible to move by a shoulder 34a of the knob 34 the drum axially of the shaft 3 through the spring 35, tubular member 36 and bearing 32. The movement of the drum 8 is interrupted as an end of the V-groove in the short cylinder 26 abuts against the rivet shaft 27, so that the drum 8 can be disposed in a predetermined position with respect to the support shaft 3.

The side walls 10 and 1d of the drum 8 are connected together by three stays 38, 39 and 40 as shown in FIG. 2 and mount thereon the cylindrical supporter 1. As aforementioned, the supply reel 6 and take-up reel 4 for the photoconductive strip 2 are disposed between the two side walls 1c and 1d. The support shaft 7 is fixed between the two side walls 10 and 1d as shown in FIG. 3, and the supply reel 6 in the form of a tubular shaft is rotatably supported through bearings 38a and 38b by the support shaft 7. The photoconductive strip 2 in roll form is supported by the supply reel 6 at one end and normally under the influence of a brake member 41 so that it is kept from rotating. As shown in FIG. 2, the brake member 41 is pivotally supported at the middle portion of the stay 38 and has one arm 41a extending beneath the supply reel 6 and disposed near to it. A bent portion 41b oriented axially of the supply reel 6 is formed at the forward end of the arm 41a and on a side edge thereof nearer to the supply reel 6. A brake shoe 42 made as of rubber or cork is disposed on a side of the bent portion 41b near to the supply reel 6. The brake member 41 has the other arm 410 which extends inwardly into the cylindrical supporter 1 and disposed at the front end in the vicinity of the inner peripheral surface of the cylindrical supporter 1.

The brake member 41 is urged by the biasing force of a spring 43 to move clockwise about stay 38 in FIG. 2. The spring 43 wound on stay 38 is connected at one end to a threaded shaft 44 threaded radially into stay 38 and at the other end to the bent portion 41b. Thus, the brake member 41 is normally urged to move clockwise about stay 38, so that the brake shoe 42 is brought into pressing engagement with the outer periphery of the roll of photoconductive strip 2 wound on the supply reel 6 to keep it from rotating inadvertently.

The take-up reel 4 disposed in a position diametrically opposite to the supply reel 6 with respect to the cylindrical supporter 1 centered at the support shaft 3 8 is supported by the support shaft 5 rotatably supported by the right and left side walls 10 and 1d of the photosensitive drum 8 and disposed therebetween. The support shaft 5 has a left end portion 5a (in FIG. 3) supported by the left end wall 1c through a bearing 45 and extending at its front end through the side wall 1c outwardly of the drum 8. The support shaft 5 has a right end portion (in FIG. 3) supported by the right side wall 1d through a one-way clutch 46, so that the support shaft 5 rotates in one direction only. When the support shaft 5 rotates in the predetermined direction, the takeup reel 4 supported thereby to act as a unit also rotates to wind on the take-up reel 4 the portion of the photoconductive strip 2 or the photoreceptor on the outer periphery of the photosensitive drum 8.

As shown in FIG. 2 and FIG. 3, the take-up reel 4 is formed substantially in the middle portion thereof with a slit 4a oriented axially of the reel 4 to receive therein a tongue 2a formed at the leading end of the photoconductive strip 2. By inserting the tongue 2a in the slit 4 when the photoconductive strip 2 is first wound on the take-up reel 4, the photoconductive strip 2 can be firmly secured to the take-up reel 4.

The supply reel 6 constructed and supported in the interior of the drum 8 as aforementioned is adapted to rotate about the support shaft 7 in the direction of an arrow a or counterclockwise as shown in FIG. 1 and FIG. 2 to feed the photoconductive strip 2 through the slit 1b to the major portion of the outer periphery of the photosensitive drum 8 while the take-up reel 4 is adapted to rotate with the support shaft 5 in the direction of an arrow b or clockwise in FIG. 1 and FIG. 2 to wind thereon the portion of the photoconductive strip 2 or the photoreceptor by moving the same through the slit la into the interior of the drum 8.

When the photoconductive strip 2 moves through the slit 1b in being paid out of the supply reel 8 or it moves through the slit 1a in being wound on the take-up reel 6, the surface of the strip which is made of an organic semi-conductor may be damaged if it scratches against edges of the outer periphery of the drum 8 forming the slits 1b and 1a. In order to keep the surface of the photoconductive strip from being damaged in this way, edges of the minor portion of the outer periphery of the drum 8 disposed in spaced juxtaposed relation to edges of the major portion of the outer periphery of the drum 8 to define therebetween the slits lb and 1a are provided with members 48 and 49 respectively which are made of rubber or other soft material.

One example of the photoconductive strip advance device of the photoreceptor changing device according to the invention as incorporated in the copying machine having the aforementioned photosensitive drum 8 will now be decribed. Secured to the left end portion 3a of the support shaft 3 extending through the cylindrical bearing housing 20 and outwardly of the left side plates 25a as shown in FIG. 3 is a drive wheel 51 over which is trained as shown in FIG. 7 a chain 70 driven at a constant rate by a synchronous motor (not shown). When the chain 70 is driven, the photosensitive drum 8 rotates clockwise in FIG. 2 about the support shaft 3 which is the drive shaft for the drum 8. The drive wheel 51 is mounted on the support shaft 3 by securing the drive shaft 51 by a rivet shaft 54 to a fixing ring 52 which in turn is secured to the support shaft 3 by a rivet shaft 53.

A drive gear 55 for the take-up reel 4 best shown in 7 FIG. 4 is secured to the fixing ring 52 by a rivet shaft 56 9 to act as a unit therewith and has a relatively large diameter. The gear 55 is slightly larger in the number of teeth than the sun gear subsequently to be described. Maintained in meshing engagement with the drive gear 55 is a transmission gear 57 rotatably supported by a shaft 59 connected to a support plate 58 secured to the outer side of the left side plate 250. The transmission gear 57 has secured to its axial center bore and disposed axially thereof a tubular shaft 57a which is supported by the shaft 59 through a cylindrical bearing 60a. Coaxially mounted on the shaft 59 and disposed adjacent the transmission shaft 57 is a connection gear 61 which also has secured to its axial center bore and disposed axially thereof a tubular shaft 610 which is supported by the shaft 59 through a cylindrical bearing 60b. The two tubular shafts 61a and 57a mounted on the shaft 59 are disposed adjacent and in contact with each other at their ends.

A coil spring 62 is mounted on the outer peripheries of the two tubular shafts 57a and 61a. One end portion 62a of the coil spring 62 on the side of the transmission gear 57 is secured to a sleeve 63a fitted over the coil spring 62 while the other end 62 thereof on the side of the connection gear 61 is wound on the tubular shaft 610 as shown in FIG. 3 and FIG. 4. The sleeve 63 is integrally formed at one end of its outer periphery with a ratchet wheel 63 oriented axially therewith for preventing tightening of the coil spring 62 when the transmission gear 57 rotates counterclockwise in the direc tion of an arrow d about the shaft 59. Maintained in engagement with one of the teeth of the ratchet wheel 63 is a pawl 640 secured to one arm of a locking member 64 pivotally supported at 64b by an immovable member (not shown) through a shaft 65 as shown in FIG. 3 and FIG. 4.

The locking member 64 is in the form of a bell crank and its other arm 646 is adapted to be pulled by a solenoid M mounted on the support plate 58. A torsion spring 66 mounted on the shaft 66 is connected at one end 66:: to the locking member 64 so as normally to urge by its biasing force the locking member 64 to rotate counterclockwise about the shaft 65,- so that the pawl 64a is maintained in engagement with one of the teeth of the ratchet wheel 63 to preclude rotation thereof.

On the other hand, the connection gear 61 is in meshing engagement with a sun gear 68 mounted on the cylindrical bearing housing 29 through a bearing 67. The connection gear 61 has a diameter slightly larger than that of the transmission gear 57 and is slightly larger in the number of teeth the transmission gear 57. However, the sun gear 68 in meshing engagement with the connection gear 61 has a diameter slightly smaller than that of the drive gear 55 and is smaller in the number of teeth than the drive gear 55. Maintained in meshing engagement with the sun gear 68 is a sheet advance gear 69 secured to the left end portion 5a of the support shaft 5 for the take-up reel 4 extending through the right end wall It outwardly of the drum 8 (leftwardly in FIG. 3).

The strip advance device of the photoreceptor changing apparatus according to the invention constructed as aforementioned operates as follows. When the drive wheel 51 is driven through the chain 70 (See FIG. 7) by the synchronous motor, the support shaft 3 for the photosensitive drum 8 to which the drive sheet 55 is secured rotates with the drive wheel 51, so that the photosensitive drum 8 rotates about the center axis 10 of the support shaft 3 in the direction of the arrow 0 as shown in FIG. 2, FIG. 4 and FIG. 5. While the drum 8 is rotating in the direction of the arrow 0, an electrophotographic copying operation is carried out by the aforementioned devices disposed around the photosensitive drum 8. Rotation of the support shaft 3 results in the drive shaft 55 rotating in the same direction as the photosensitive drum 8, so that the transmission gear 57 in meshing engagement with the drive shaft 55 rotates in the direction of the arrow d as shown in FIG. 4 and FIG. 5. Even if the gear 57 rotates counterclockwise (See FIG. 5), the coil spring 62 is not tightened because rotation of the ratchet wheel 63 is prevented by the pawl 64a. Thus, rotation of the gear 57 is not transmitted to the connection gear 61.

On the other hand, rotation of the photosensitive drum 8 results in the take-up reel 4 rotating with the drum 8, so that the sheet advance gear 69 revolves around the sun gear 68. Revolution of the gear 69 around the sun gear 68 causes the latter to rotate about the support shaft 3 clockwise or in the direction of an arrow e as shown in FIG. 4 and FIG. 6. Rotation of the sun gear 68 causes the connection gear 61 to rotate in the direction of an arrow f in FIG. 6 about the shaft 59. The direction in which the connection gear 61 rotates is the same as the direction of rotation of the transmission gear 57 or the direction in which the coil spring 62 is loosened. Since the diameter of the sun gear 68 is smaller than that of the drive gear 55, the rate of rotation of the connection gear 61 is lower than that of the transmission gear 57.

The photosensitive drum 8 operates as aforementioned to perform an electrophotographic copying operation when makes one revolution. After performing about 5,000 copying operations, the portion of the photoconductive strip 2 or the photoreceptor on the major portion of the outer periphery of the photosensitive drum 8 is fatigued and should be replaced by a new photoreceptor. When it is desired to effect a change of the photoreceptor, a current is passed to the solenoid M which is energized and pulls the other arms 64c of the locking member 64 toward the solenoid M. This results inthe locking member 64 moving clockwise in FIG. 5 about the shaft 65, so that the pawl 64a is released from engagement with one of the teeth of the ratchet wheel 63. This leaves the ratchet wheel 63 and sleeve 63a free to move, so that rotation of the transmission gear 57 quickly tightens the coil spring 62. As a result, the transmission gear 57 and connection gear 61 operates as a unit and high speed rotation of the transmission gear 57 is transmitted to the sun gear 68 through the connection gear 61, so that the sun gear 68 is rotated by the connection gear 61.

The sun gear 68 is designed such that its rate of rotation is slightly higher than that of the photosensitive drum 8. That is, the connection gear 61 has a diameter greater than that of the transmission gear 57. Thus, when rotation of the transmission gear 57 is transmitted to the connection gear 61, the sun gear 68 rotates at a rate slightly higher than the drum 8. When the sun gear 8 rotates at a higher rate, the sheet advance gear 69 in meshing engagement with the sun gear 68 as a planetary gear begins to rotate about the center axis of the shaft 5 clockwise or in the direction of the arrow b in FIG. 6 while revolving around the sun gear 68. Rotation of the sheet advance gear 69 about the shaft 5 results in the take-up reel 4 rotating clockwise with the shaft 5, so that the portion of the photoconductive sheet 2 or the photoreceptor on the outer periphery of the drum 8 is moved and withdrawn through the slit 1a into the interior of the drum 8 and wound on the takeup reel 4. At this time, the strip advance gear 69 is rotated by the difference in the rate of rotation between the sun gear 68 and the photosensitive drum 8 and its rate of rotation is greatly reduced, so that the gear 69 can exert a high force during its rotation. Thus, the portion of the photoconductive strip 2 maintained in intimate contact with the outer periphery of the drum 8 can be readily advanced therealong.

As the take-up reel 4 rotates to wind the photoconductive strip 2 thereon, the supply reel 6 also rotates in the direction of the arrow a in FIG. 2 against the braking force of the brake member 41, so that a new portion of the photoconductive sheet 2 of a new photoreceptor is fed through the slit 1b to the major portion of the outer periphery of the drum 8. When the old photoreceptor is replaced by the new photoreceptor, a current passed to the solenoid M is cut off to de-energize the same. This brings the pawl 64a into engagement with one of the teeth of the ratchet wheel 63 which stops rotating, so that the coil spring 62 is loosened and the transmission gear 57 and connection gear 61 are released from engagement. Thus, no rotation is transmitted from gear 57 to gear 61 and accordingly transmission of rotation from the sun gear 68 to the strip advance gear 69 is interrupted. Thus, gear 69 is kept form rotating about the shaft and revolves around the sun gear 58 again.

From the foregoing description, it will be appreciated that the present invention eliminates the gearing disposed in the interior of the photosensitive drum in conventional electrophotographic copying machines and provides instead a strip advance device, compact in size, which is disposed near the drum 8. This permits the size and weight of the photosensitve drum to be greatly reduced while enabling to obtain a high force for advancing the photoconductive strip to wind the same on the take-up reel.

The device for feeding a photoconductive sheet in a predetermined length according to the invention wil now be described. The device comprises counter means whichis adapted to be actuated in conjunction with the advancing of the portion of photoconductive strip or the photoreceptor on the outer periphery of the photosensitive drum 8 and the winding thereof on the take-up reel 4 of the strip advance device described above, so as to determine the time at which the current being passed to the solenoid M should be cut off. By controlling the time at which the current to the solenoid is cut off, it is possible to feed a predetermined length of the photoconductive sheet 2 to the outer periphery of the photosensitive sheet 8 at all times.

The construction and operation of the controller and the counter means will now be described in detail. As shown in FIG. 7, a shaft 71 disposed parallel to the drum support shaft 3 has mounted thereon, through bearings 74 and 75 as shown in FIG. 8, a controller 72 formed on its outer periphery with a protuberance 72a and a ratchet wheel 73 respectively. The controller 72 is maintained in engagement with the ratchet wheel 73 by a spring clutch which comprises a coil spring 76 mounted between controller 72 and ratchet wheel 73 and a clutch actuation plate 77 in the form of a disc formed integrally on the outer periphery of a sleeve 77a covering the coil spring 76 and formed therein with a cutout 7712 as shown in FIG. 7.

The coil spring 76 is connected at one end 76a to the controller 72 and at the other end 76b to the sleeve 77a. As shown in FIG. 7, the ratchet wheel 73 is adapted to be rotated in the direction of an arrow j by an advance pawl 78 mounted at the end of one arm of a bell-crank pivotally supported by a shaft 79 disposed parallel to the drum support shaft 3 and normally urged into engagement with one of the teeth of the ratchet wheel 73 by the biasing force of a spring (not shown). The other arm 80b of the bell-crank 80 extends toward the drive wheel 51 and is formed therein with a longitudinally oriented slot 800 receiving therein a pin 82 planted on a chain wheel 83 rotatably supported by a shaft 81 disposed to the drum support shaft 3.

The endless chain 70 trained over the drive wheel 51 is also trained over the chain wheel 83 and rotates the chain wheel 83 in the direction of an arrow h about shaft 81 when actuated. Rotation of the chain wheel 83 results in the pin 82 rotating with the wheel 83 about shaft 81, so that the bell-crank is oscillated in the directions of arrows [about shaft 79 by the pin and slot combination and the advance pawl 78 intermittently advances the ratchet wheel 73 in the direction of the arrow j tooth by tooth.

On the other hand, a lock pawl 84a is in engagement with the cutout 77b in the actuation plate and mounted at the end of one arm 84b of a bell-crank 84 pivotally supported by a shaft 85. A compression coil 86 is connected at one end to the other arm 84c of the bellcrank 84 and at the other end to an immovable member (not shown) to urge the bell-crank 84 normally to move clockwise about shaft by its biasing force. However, the clockwise movement of the bell-crank 84 is precluded by the lock pawl 84a engaging the cutout 77b. The other arm 84c of the bell-crank is adapted to be pulled by a solenoid M1 in a direction opposite to the direction in which it is moved by spring 86.

A current is passed to solenoid M1 simultaneously as a current is passed to solenoid That is, a photoconductive strip advance command signal is supplied to the two solenoids M and M1. The controller 72 is in the form of a disc fonned on its periphery with the projection 72a which moves along a path in which a microswitch S1 for cutting off the supply of current to the solenoids is disposed. The microswitch S1 is disposed in a position in which the projection 72a depresses an actuator Sla of the microswitch S1 immediately before the controller 72 completes its one revolution. The position in which the switch S1 is disposed is automatically moved, however, toward the starting position of the protuberance 72a each time the photoconductive strip is advanced or the photoreceptor is changed. The movement of the switch S1 is intended to correct an error in the length of the photoconductive strip advanced and wound on the take up reel 4 which might otherwise occur due to an increase in the diameter of the strip wound take-up reel which grows each time the strip is advanced. The microswitch S1 is mounted on a movable member.

More specifically, the microswitch S1 is mounted, as shown in FIG. 9, on a free end portion 88b of a switch mount 88 which is pivotally supported at a base 88a by shaft 71 to act as a swit h actuation position controller. In the embodiment shown and described herein, replacing of the first position of photoconductive strip or first photoreceptor on the outer periphery of the photosensitive drum 8 by the next following portion of photo- 13 conductive strip or next following photoreceptor is completed when the protuberance 72a has made a three-quarter revolution about shaft 71. Thus, the switch mounted 88 is adjusted such that the microswitch S1 is initially disposed in this position.

The switch mount 88 is normally urged to move clockwise about shaft 71 by the biasing force of a spring 89 shown in FIG. 9, but its movement is precluded by a cam 90 secured to a shaft 91 disposed parallel to the drum support shaft 3 and mounting thereon a ratchet wheel 92 functioning as a counter operatively associated with the controller 72 and adapted to be actuated upon termination of rotation thereof. The ratchet wheel 92 is formed on its periphery with teeth corresponding in number to portions of the photoconductive strip 2 wound in roll form on the supply reel 6 (See FIG. 2) and adapted to be paid out thereof to act as photoreceptors on the outer periphery of the photosensitive drum 8. That is, if the photoconductive strip 2 has a length sufficiently large to supply photoreceptors to the photosensitive drum 8, then the ratchet wheel 92 has 15 teeth.

The ratchet wheel 92 constructed as aforementioned is adapted to be moved tooth by tooth by an advance pawl 93 in the direction of an arrow m or counterclockwise about shaft 91 as the controller 72 having the projection 72a makes one complete revolution. The advance pawl 93, which is mounted at the end of one arm 94a of an advance lever 94, is urged by the biasing force of a spring 95 into engagement with one of the teeth of ratchet wheel 92. The advance lever 94, which is pivotally supported by shaft 91, is normally urged by the biasing force of a spring 98 to move clockwise about shaft 91, and the other arm 94b thereof extends between the controller 72 and actuation plate 77. The other arm 94b has an end portion disposed in the path of movement of a pin 96 planted on an inner end surface of the controller 72 and projecting toward the actuation plate 77 to be normally maintained in engagement with the end portion of the other arm 94b. Thus, when the controller 72 provided with the projection 72 a makes one complete revolution, the other arm 94b of advance lever 94 is pushed and moved by the pin 96, so that the lever 94 oscillates about shaft 91 and allows the advance pawl 93 to move the-ratchet wheel 92 by one tooth. Another pawl 97 shown in engagement with the ratchet wheel 92 performs the function of preventing reverse movement of the ratchet wheel.

The device for feeding a photoconductive strip is a predetermined length provided with the counter means constructed as aforementioned operates as follows. The device remains inoperative when a electrophotographic copying operation is performed by the photosensitive drum 8 (See FIG. 1 and FIG. 2). That is, when the chain wheel 83 is rotated in the direction of the arrow 12 by the drum support shaft 3 through the endless chain 70 and the bell-crank 80 is urged to oscillates in the direction of the arrow l to cause the advance pawl 78 to move the ratchet wheel 73 in the direction of the arrow j, the spring clutch is disengaged because the lock pawl 84a is in engagement with the cutout 77b in the actuation plate 77. Thus, the ratchet wheel 73 only rotates in the direction of the arrow j.

If a photoconductive sheet advance command signal is produced and supplied to solenoids M and M1, then the lock pawl 64is released from engagement with the cutout 77b, so that the transmission gear 57 is connected to the connection gear 61 by clutch action and the sheet advance gear 69 shown in FIG. 4 begins to rotate about shaft 5 to initiate winding on the take-up reel 4 the portion of photoconductive strip on the outer periphery of the photoconductive drum 8. At the same time, rotation of the ratchet wheel 73 in the direction of the arrow j is transmitted to the controller 72 to rotate the same in the same direction as the ratchet wheel 73 through the engaged spring clutch (FIG. 8).

More specifically, energization of solenoid M1 re sults in the other arm 840 of the bell-crank 84 being pulled toward the solenoid, so that the bell-crank 84 pivots counter clockwise about shaft and the lock pawl 84a is released from engagement with the cutout 77b in the actuation plate 77. As a result, the spring clutch is engaged to connect the ratchet wheel 73 to the controller 72. Thus, rotation of the ratchet wheel 73 is transmitted to the controller 72 and the two elements act as a unit as the former intermittently rotates clockwise about shaft 71. Rotation of the controller 72 with the ratchet wheel 73 releases the pin 96 from engagement with the other arm 94b of the feed lever 94, so that the lever 94 is urged to move clockwise about shaft 91 by the biasing force of spring 98. This causes the advance pawl 93 to be released from engagement with the tooth and brought into engagement with the preceding tooth of the ratchet wheel 92. The photoconductive strip 2 is advanced while the feed pawl 93 remains in this position. When advance movement of the strip is finished, the controller 72 has substantially made a three-quarter revolution, so that its projection 72a depresses the actuator Sla and actuates the switch S1 to thereby cut off the supply of current to solenoids M and M1. Upon cutting off the supply of current to solenoid M, the lock pawl 64a is brought into engagement with one of the teeth of ratchet wheel 63. This cuts off transmission of rotation from the transmission gear 57 to the connection gear 61, with the result that the sheet advance gear 69 stops rotating about shaft 5 and advance of the photosensitive strip 2 is finished.

Upon cutting off of the supply of current to solenoid M1, the bell-crank 84 tries to pivot clockwise about shaft 85 by virtue of the biasing force of spring 86 and return to its initial position. However, the cutout 77b formed in the actuation plate 77 rotating with the ratchet wheel 73 as a unit is not disposed at this time in a position corresponding to the position in which the lock pawl 84a is disposed. Accordingly, rotation of the ratchet wheel 73 is transmitted to the actuation plate 77 and controller 72 even if the supply of current to solenoid M1 is cut off, so that they continue to rotate.

Immediately before the controller 72 completes it one revolution, the other arm 94b of the advance lever 94 is moved upwardly by the pin 96 and the advance lever 94 is pivoted counter clockwise about shaft 91 against the biasing force of spring 98. Thus, the advance pawl 93 moves the ratchet wheel 92 by one tooth in the direction of the arrow m. The time at which movement of the ratchet wheel 92 in the indicated direction finishes coincides with the time at which the controller 72 has made one complete revolution about shaft 71, and the cutout 77b is positioned against the lock pawl 84a. This automatically brings the latter into engagement with the former and interrupts transmis sion of rotation from the ratchet wheel 73 to the controller.

On the other hand, if the ratchet wheel 92 is moved by one tooth in the direction of arrow m, then the support 91 on which it is secured angularly rotates in the same direction and the cam 90 secured to shaft 91 also rotates angularly through the same angle as shaft 91. Angular rotation of cam 90 results in the peripheral cam surface thereof moving the switch mount 88 counterclockwise about shaft 71 against the biasing force of spring 89 as shown in FIG. 9. This counterclockwise movement of switch mount 88 shifting the microswitch S1 mounted thereon to a position in which the actuator Sla therefor is depressed, when the controller 72 rotates, by the projection 72a thereon earlier than it was depressed in the previous strip advance operation. Thus, the microswitch S1 is actuated earlier in the next strip advance operation than in the previous operation. Earlier actuation of the microswitch in each operation than in the previous operation means that the time interval during which solenoids M and M1 are energized is shortened in each operation than in the previous operation. This necessarily reduces the angle through which the take-up reel 4 rotates in each operation. Thus, the increase in the length of the strip advanced and wound on the take-up reel as the diameter of the strip wound take-up reel increases, which would take place if the take-up reel were to rotate through the same angle at all times, can be compensated for by reducing the angle of rotation of the take-up shaft, thereby enabling the photoconductive strip to be fed in a predetermined length at all times.

The cam 90 is constructed such that its peripheral cam surface for varying the position in which microswitch S1 is actuated each time a photoconductive strip advance operation is performed is designed such that the diameter of the cam is gradually increased. The curve of increase in diameter is designed to correspond to the increase in the diameter of the strip wound takeup reel, and the maximum diameter portion of the cam depresses the switch mount 88 as shown in dash-anddot lines in FIG. 10 when the last but one or fourteenth portion of photoconductive strip 2 on the photosensitive drum 8 is advanced and wound on the take-up reel.

From the foregoing description, it will be appreciated that the device for feeding a photoconductive strip in a predetermined length according to the invention precludes winding of the photoconductive strip on the take-up reel in a greater length than is needed, which might otherwise be the case when the diameter of the strip wound take-up reel increases if the take-up reel is rotated through the same angle of rotation in spite of the increase in the diameter of the strip wound take-up reel, by moving the actuation position of the micro switch S1. This permits the photoconductive strip to be fed in a predetermined length to the outer periphery of the photosensitive drum at all times. The invention offers the advantage of allowing to obtain an overall compact size and a light weight in the photosensitive drum because no sensing means is provided in the interior of the photosensitive drum itself and the photoconductive strip advance device and the device for feeding a photoconductive strip in a predetermined length are all provided outside the drum and operatively to the drive system for the photosensitive drum.

Means for indicating the length of the residual photoconductive strip on the supply reel, which is operatively associated with the aforementioned device for feeding a photoconductive strip in a predetermined length, will now be described. The means comprises a pointer 99 mounted on the shaft 91 to which the ratchet wheel 92 is secured, and a dial 100 in disc fonn calibrated in numbers of portions of the photoconductive strip wound on the supply reel which will serve as photoreceptors on the outer periphery of the photosensitive drum as shown in FIG. 7. The ratchet wheel 92 of the device for feeding a photoconductive strip in a predetermined length is formed with teeth corresponding in number to the number of portions of the photoconductive strip on the supply reel which will serve as photoreceptors in the photosensitive drum and advanced tooth by tooth by the advance lever each time the portion of the photoconductive strip on the outer periphery of the photosensitive drum is advanced or the photoreceptor is changed. Thus, the ratchet wheel 92 and advance lever 94 function as a sort of counter. As the ratchet wheel 92 moves intermittently, the shaft 91 supporting the same angularly rotates. The pointer 99 of means for indicating the length of residual strip is secured to shaft 91 and adapted to cooperate with the dial 100 having digits printed on the outer marginal portion for indicating the number of portions of the strip. Needless to say, the pointer 99 and dial 100 are diposed in a position which can readily be seen by the operator.

As can be readily seen from the aforementioned description of the operation of the ratchet wheel 92, the position of the pointer 99 on the dial 100 shifts from one digit to another as the photoconductive strip is advanced, thereby indicating the number of portions of the photoconductive strip on the supply reel which will serve as photoreceptors. Thus, when the pointer 99 is indexed with the digit 0, it shows that no photoconductive sheet is wound on the supply reel.

The pointer 99 is shown and described above as being directly mounted on shaft 91. The invention is not limited to this form of indication means, and any other indication means may be employed. For example, a pinion in meshing engagement with rack may be mounted on shaft 91 and the pointer may be mounted on the rack, so that the calibration can be provided on a ,bar, not on a-disc. Alternatively, a discal indication plate may be secured to shaft 91 so that the graduation thereon can be seen through a window from outside.

The provision of means for indicating the length of the residual strip on the supply reel according to the invention permits the number of portions of the photoconductive strip on the supply reel which will serve as photoreceptors on the photosensitive drum to be indicated readily by operatively associating the pointer or the graduation with the device for feeding a photoconductive strip in a predetermined length.

Finally, means for detecting the exhaustion of a photoconductive strip on the supply reel will be described. The means is operatively associated with the aforementioned means for indicating the length of residual strip on the supply reel and comprises a microswitch S2 and an actuator 101 therefore as shown in FIG. 7. The actuator 101 is secured at its center to shaft 91 and has formed on its outer periphery a protuberance 101a which is disposed in a position corresponding to the 17 photoreceptor, so that the switch can produce a strip exhaustion signal. An indication lamp may be turned on or a buzzer may be sounded when the switch produces a signal.

As aforementioned, the means for detecting the exhaustion of strip on the supply reel according to the invention is operatively associated with the means for indicating the length of the residual strip on the supply reel which in turn is operatively associated with the device for feeding a photoconductive strip in a predetermined length. This permits the photoreceptor changing apparatus to be formed as a unit and detachably mounted on an electrophotographic copying machine using a photosensitive drum, and to be operated without relying on sensing means provided in the photosensitive drum.

While the invention has been described with reference to a preferred embodiment thereof, it is to be understood that the invention is not limited to the specific form of the embodiment and that many modifications and changes may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A photoreceptor changing apparatus comprising a supply reel rotatably mounted in the interior of a cylindrical supporter and having mounted thereon in roll form a photoconductive strip made of a pliable material and adapted to be paid out and applied to the outer periphery of said cylindrical supporter to serve as a photoreceptor on which an image of an original to be duplicated is formed for transfer printing on copy sheets, a take-up reel rotatably mounted in the interior of said cylindrical supporter and adapted to have said photoconductive strip wound thereon, and a photoconductive strip advance device disposed outside said cylindrical supporter and operated by a drive for rotating the cylindrical supporter to rotate said take-up reel and advance the photoconductive strip so that a portion thereof serving as a photoreceptor on the outer periphery of the photosensitive drum can be replaced by the next following portion thereof to thereby changethe photoreceptors, wherein said photoconductive strip advance device comprises a drive gear for rotating said take-up reel secured to a drive shaft for said photosensitive drum, a transmission gear in meshing engagement with said drive gear, a connection gear coaxially mounted with said transmission gear, clutch means interposed between said transmission gear and said connection gear, a sun gear mounted on said drive shaft and maintained in meshing engagement with said connection gear, and a photoconductive strip advance gear secured to said take-up reel and maintained in meshing engagement with said sun gear, said strip advance gear normally revolving around said sun gear as said photosensitive drum is rotated, rotation of said transmission gear being transmitted through said connection gear to said sun gear when said clutch is engaged to produce a difierence in the number of revolutions between said sun gear and said photosensitive drum, so that said strip advance gear is made to revolve on its own axis by said differential rotation to thereby advance the photoconductive strip and wind on the take-up reel the portion of the photoconductive strip on the outer periphery of the photosensitive drum.

2. A photoreceptor changing apparatus according to claim 1 wherein said connection gear in meshing engagement with said sun gear has a diameter larger than that of said transmission gear in meshing engagement 18 with said drive gear, and said sun gear has a diameter smaller than that of said drive gear, whereby rotation is reduced in rate and transmitted to said strip advance gear.

3. A photoreceptor changing apparatus comprising a supply reel rotatably mounted in the interior of a cylindrical supporter and having mounted thereon in roll form a photoconductive strip made of a pliable material and adapted to be paid out and applied to the outer periphery of said cylindrical supporter to serve as a photoreceptor on which an image of an original to be duplicated is formed for transfer printing on copy sheets, a take-up reel rotatably mounted in the interior of said cylindrical supporter and adapted to have said photoconductive strip wound thereon, and a photoconductive strip advance device disposed outside said cylindrical supporter and operated by a drive for rotating the cylindrical supporter to rotate said take-up reel and advance the photoconductive strip so that a portion thereof serving as a photoreceptor on the outer periphery of the photosensitive drum can be replaced by the next following portion thereof to thereby change the photoreceptors, further comprising a device for feeding a photoconductive strip in a predetermined length, comprising a controller adapted to rotate on conjunction with said take-up reel when the latter is rotated and the portion of the photoconductive strip on the outer periphery of the photosensitive drum is wound thereon, a switch adapted to be actuated by said controller as the latter rotates and interrupt the rotation of said take-up reel, counter means adapted to be actuated in conjunction with said controller at the termination of rotation thereof, and a switch mount coupled to said counter means for adjustably supporting said switch to shift the position in which the switch is actuated.

4. A photoreceptor according to claim 3 wherein said controller is intermittently connected, through a spring clutch, to a ratchet wheel coupled to said drive shaft for said photosensitive drum and adapted to rotate angularly intermittently.

5. A photoreceptor changing apparatus according to claim 3 wherein said controller is in the form of a disc formed on its outer periphery with protuberance for opening and closing said switch for controlling the rotation of said take-up reel.

6. A photoreceptor changing apparatus according to claim 3 wherein said counter means comprises a ratchet wheel formed thereon with teeth corresponding in number to portions of the photoconductive strip wound in roll form on said supply reel and serving as photoreceptors when disposed on the outer periphery on the photosensitive drum, and an advance pawl in meshing engagement with one of the teeth of the ratchet wheel and adapted to pivot at the termination of rotation said controller to advance the ratchet wheel tooth by tooth.

7. A photoreceptor changing apparatus according to claim 3 wherein said switch for controlling the rotation of said take-up reel is secured to said switch mount pivotally supported by a shaft supporting said controller.

8. A photoreceptor changing apparatus according to claim 3 wherein said switch mount is fitted at its base over a shaft supporting said controller and has a free end portion which is adapted to pivot about said controller support shaft.

9. A photoreceptor changing apparatus according to claim 8 wherein said pivotal movement of said switch mount is precluded by a cam secured to a shaft supporting a ratchet wheel formed with teeth equal in number to the portions of the photoconductive strip on the supply reel.

10. A photoreceptor changing apparatus comprising a supply reel rotatably mounted in the interior of a cylindrical supporter and having mounted thereon in roll form a photoconductive strip made of a pliable material and adapted to be paid out and applied to the outer periphery of said cynlindrical supporter to serve as a photoreceptor on which an image of an original to be duplicated is formed for transfer printing on copy sheets, a take-up reel rotatably mounted in the interior of said cylindrical supporter and adapted to have said photoconductive strip wound thereon, and a photoconductive strip advance device disposed outside said cylindrical supporter and operated by a drive for rotating the cylindrical supporter to rotate said take-up reel and advance the photoconductive strip so that a portion thereof serving as a photoreceptor on the outer periphery of the photosensitive drum can be replaced by the next following portion thereof to thereby change the photoreceptors, further comprising: a device for feeding a photoconductive strip in a predetermined length, comprising a controller adapted to rotate in conjunction with said take-up reel when the latter is rotated and the portion of the photoconductive strip on the outer periphery of the photosensitive drum is wound thereon, a switch adapted to be actuated by said controller as the latter rotates to interrupt the rotation of said take-up reel, counter means adapted to be actuated in conjunction with said controller at the tennination stage of rotation thereof, and a switch mount coupled to said counter means for adjustably supporting switch to shift the actuation position of the switch; and means for indicating the length of the residual photoconductive strip on said supply reel comprising members coupled to.said counter means and adapted to be actuated at the termination of each operation of said counter means to indicate the length or the number of portions of the residual photoconductive strip on the supply reel which will serve as photoreceptors on the outer periphery of the photosensitive drum.

11. A photoreceptor according to claim 10 wherein said means for indicating the length of the residual photoconductive strip on the supply reel comprises a pointer mounted on a shaft supporting a ratchet wheel formed thereon with teeth equal in number to the number of portions of the photoconductive strip on the supply reel which will serve as photoreceptors on the outer periphery of the photoconductive drum, and an indication plate graduated in the number of portions of the photoconductive strip on the supply reel.

12. A photoreceptor changing apparatus comprising a supply reel rotatably mounted in the interior of a cylindrical supporter and having mounted thereon in roll form a photoconductive strip made of a pliable material and adapted to be paid out and applied to the outer periphery of said cylindrical supporter to serve as a photoreceptor on which an image of an original to be duplicated is formed for transfer printing on copy sheets, a take-up reel rotatably mounted in the interior of said cylindrical supporter and adapted to have said photoconductive strip wound thereon, and a photoconductive strip advance device disposed outside said cylindrical supporter and operated by a drive for rotating the cylindrical supporter to rotate said take-up reel and advance the photoconductive strip so that a portion thereof serving as a photoreceptor on the outer periphery of the photosensitive drum can be replaced by the next following portion thereof to thereby change the photoreceptors, further comprising a device for feeding a photoconductive strip in a predetermined length, comprising a controller adapted to rotate in conjunction with said take-up reel when the latter is rotated and the portion of the photoconductive strip on the outer periphery of the photosensitive drum is wound thereon, a switch adapted to be actuated by said controller as the latter rotates to interrupt the rotation of said take-up reel, counter means adapted to be actuated in conjunction with said controller at the termination of rotation thereof, and a switch'mount coupled to said counter means for adjustably supporting said switch to shift the actuation position of the switch; means for indicating the length of the residual photoconductive strip on said supply reel coupled to said counter means and adapted to be actuated at the termination of each operation of said counter means to indicate the length or the number of portions of the residual photoconductive strip on the supply reel which will serve as photoreceptors on the outer periphery of the photosensitive drum; and means for detecting the exhaustion of the photoconductive strip on the supply reel operatively associated with said means for indicating the length of the residual photoconductive strip on the supply reel and comprising a switch adapted to be actuated when said counter means counts the last portion of the photoconductive strip on the supply reel and produce a signal informing that that the photoconductive strip on the supply reel is exhausted.

13. A photoreceptor changing apparatus according to claim 12 wherein said switch for producing a photoconductive strip exhaustion signal is adapted to be opened and closed by an actuator mounted on a shaft on which a ratchet wheel formed with teeth equal in number to the portions of the photoconductive strip on the supply reel is supported.

14. A photoreceptor changing apparatus according to claim 13 wherein said actuator is in disc form formed on its outer periphery with a protuberance. 

1. A photoreceptor changing apparatus comprising a supply reel rotatably mounted in the interior of a cylindrical supporter and having mounted thereon in roll form a photoconductive strip made of a pliable material and adapted to be paid out and applied to the outer periphery of said cylindrical supporter to serve as a photoreceptor on which an image of an original to be duplicated is formed for transfer printing on copy sheets, a take-up reel rotatably mounted in the interior of said cylindrical supporter and adapted to have said photoconductive strip wound thereon, and a photoconductive strip advance device disposed outside said cylindrical supporter and operated by a drive for rotating the cylindrical supporter to rotate said take-up reel and advance the photoconductive strip so that a portion thereof serving as a photoreceptor on the outer periphery of the photosensitive drum can be replaced by the next following portion thereof to thereby change the photoreceptors, wherein said photoconductive strip advance device comprises a drive gear for rotating said take-up reel secured to a drive shaft for said photosensitive drum, a transmission gear in meshing engagement with said drive gear, a connection gear coaxially mounted with said transmission gear, clutch means interposed between said transmission gear and said connection gear, a sun gear mounted on said drive shaft and maintained in meshing engagement with said connection gear, and a photoconductive strip advance gear secured to said take-up reel and maintained in meshing engagement with said sun gear, said strip advance gear normally revolving around said sun gear as said photosensitive drum is rotated, rotation of said transmission gear being transmitted through said connection gear to said sun gear when said clutch is engaged to produce a difference in the number of revolutions between said sun gear and said photosensitive drum, so that said strip advance gear is made to revolve on its own axis by said differential rotation to thereby advance the photoconductive strip and wind on the take-up reel the portion of the photoconductive strip on the outer periphery of the photosensitive drum.
 2. A photoreceptor changing apparatus according to claim 1 wherein said connection gear in meshing engagement with said sun gear has a diameter larger than that of said transmission gear in meshing engagement with said drive gear, and said sun gear has a diameter smaller than that of said drive gear, whereby rotation is reduced in rate and transmitted to said strip advance gear.
 3. A photoreceptor changing apparatus comprising a supply reel rotatably mounted in the interior of a cylindrical supporter and having mounted thereon in roll form a photoconductive strip made of a pliable material and adapted to be paid out and applied to the outer periphery of said cylindrical supporter to serve as a photoreceptor on which an image of an original to be duplicated is formed for transfer printing on copy sheets, a take-up reel rotatably mounted in the interior of said cylindrical supporter and adapted to have said photoconductive strip wound thereon, and a photoconductive strip advance device disposed outside said cylindrical supporter and operated by a drive for rotating the cylindrical supporter to rotate said take-up reel and advance the photoconductive strip so that a portion thereof serving as a photoreceptor on the outer periphery of the photosensitive drum can be replaced by the next following portion thereof to thereby change the photoreceptors, further comprising a device for feeding a photoconductive strip in a predetermined length, comprising a controller adapted to rotate on conjunCtion with said take-up reel when the latter is rotated and the portion of the photoconductive strip on the outer periphery of the photosensitive drum is wound thereon, a switch adapted to be actuated by said controller as the latter rotates and interrupt the rotation of said take-up reel, counter means adapted to be actuated in conjunction with said controller at the termination of rotation thereof, and a switch mount coupled to said counter means for adjustably supporting said switch to shift the position in which the switch is actuated.
 4. A photoreceptor according to claim 3 wherein said controller is intermittently connected, through a spring clutch, to a ratchet wheel coupled to said drive shaft for said photosensitive drum and adapted to rotate angularly intermittently.
 5. A photoreceptor changing apparatus according to claim 3 wherein said controller is in the form of a disc formed on its outer periphery with protuberance for opening and closing said switch for controlling the rotation of said take-up reel.
 6. A photoreceptor changing apparatus according to claim 3 wherein said counter means comprises a ratchet wheel formed thereon with teeth corresponding in number to portions of the photoconductive strip wound in roll form on said supply reel and serving as photoreceptors when disposed on the outer periphery on the photosensitive drum, and an advance pawl in meshing engagement with one of the teeth of the ratchet wheel and adapted to pivot at the termination of rotation said controller to advance the ratchet wheel tooth by tooth.
 7. A photoreceptor changing apparatus according to claim 3 wherein said switch for controlling the rotation of said take-up reel is secured to said switch mount pivotally supported by a shaft supporting said controller.
 8. A photoreceptor changing apparatus according to claim 3 wherein said switch mount is fitted at its base over a shaft supporting said controller and has a free end portion which is adapted to pivot about said controller support shaft.
 9. A photoreceptor changing apparatus according to claim 8 wherein said pivotal movement of said switch mount is precluded by a cam secured to a shaft supporting a ratchet wheel formed with teeth equal in number to the portions of the photoconductive strip on the supply reel.
 10. A photoreceptor changing apparatus comprising a supply reel rotatably mounted in the interior of a cylindrical supporter and having mounted thereon in roll form a photoconductive strip made of a pliable material and adapted to be paid out and applied to the outer periphery of said cynlindrical supporter to serve as a photoreceptor on which an image of an original to be duplicated is formed for transfer printing on copy sheets, a take-up reel rotatably mounted in the interior of said cylindrical supporter and adapted to have said photoconductive strip wound thereon, and a photoconductive strip advance device disposed outside said cylindrical supporter and operated by a drive for rotating the cylindrical supporter to rotate said take-up reel and advance the photoconductive strip so that a portion thereof serving as a photoreceptor on the outer periphery of the photosensitive drum can be replaced by the next following portion thereof to thereby change the photoreceptors, further comprising: a device for feeding a photoconductive strip in a predetermined length, comprising a controller adapted to rotate in conjunction with said take-up reel when the latter is rotated and the portion of the photoconductive strip on the outer periphery of the photosensitive drum is wound thereon, a switch adapted to be actuated by said controller as the latter rotates to interrupt the rotation of said take-up reel, counter means adapted to be actuated in conjunction with said controller at the termination stage of rotation thereof, and a switch mount coupled to said counter means for adjustably supporting switch to shift the actuation position of the switch; and means for indicating the length of the residual pHotoconductive strip on said supply reel comprising members coupled to said counter means and adapted to be actuated at the termination of each operation of said counter means to indicate the length or the number of portions of the residual photoconductive strip on the supply reel which will serve as photoreceptors on the outer periphery of the photosensitive drum.
 11. A photoreceptor according to claim 10 wherein said means for indicating the length of the residual photoconductive strip on the supply reel comprises a pointer mounted on a shaft supporting a ratchet wheel formed thereon with teeth equal in number to the number of portions of the photoconductive strip on the supply reel which will serve as photoreceptors on the outer periphery of the photoconductive drum, and an indication plate graduated in the number of portions of the photoconductive strip on the supply reel.
 12. A photoreceptor changing apparatus comprising a supply reel rotatably mounted in the interior of a cylindrical supporter and having mounted thereon in roll form a photoconductive strip made of a pliable material and adapted to be paid out and applied to the outer periphery of said cylindrical supporter to serve as a photoreceptor on which an image of an original to be duplicated is formed for transfer printing on copy sheets, a take-up reel rotatably mounted in the interior of said cylindrical supporter and adapted to have said photoconductive strip wound thereon, and a photoconductive strip advance device disposed outside said cylindrical supporter and operated by a drive for rotating the cylindrical supporter to rotate said take-up reel and advance the photoconductive strip so that a portion thereof serving as a photoreceptor on the outer periphery of the photosensitive drum can be replaced by the next following portion thereof to thereby change the photoreceptors, further comprising a device for feeding a photoconductive strip in a predetermined length, comprising a controller adapted to rotate in conjunction with said take-up reel when the latter is rotated and the portion of the photoconductive strip on the outer periphery of the photosensitive drum is wound thereon, a switch adapted to be actuated by said controller as the latter rotates to interrupt the rotation of said take-up reel, counter means adapted to be actuated in conjunction with said controller at the termination of rotation thereof, and a switch mount coupled to said counter means for adjustably supporting said switch to shift the actuation position of the switch; means for indicating the length of the residual photoconductive strip on said supply reel coupled to said counter means and adapted to be actuated at the termination of each operation of said counter means to indicate the length or the number of portions of the residual photoconductive strip on the supply reel which will serve as photoreceptors on the outer periphery of the photosensitive drum; and means for detecting the exhaustion of the photoconductive strip on the supply reel operatively associated with said means for indicating the length of the residual photoconductive strip on the supply reel and comprising a switch adapted to be actuated when said counter means counts the last portion of the photoconductive strip on the supply reel and produce a signal informing that that the photoconductive strip on the supply reel is exhausted.
 13. A photoreceptor changing apparatus according to claim 12 wherein said switch for producing a photoconductive strip exhaustion signal is adapted to be opened and closed by an actuator mounted on a shaft on which a ratchet wheel formed with teeth equal in number to the portions of the photoconductive strip on the supply reel is supported.
 14. A photoreceptor changing apparatus according to claim 13 wherein said actuator is in disc form formed on its outer periphery with a protuberance. 